Pressure switch



Dec. 2l, 1948.

N. J. sMlTH i PRESSURE SWITCH Filed April 12, 1946 mi WS Iaveza'vaf.- Mfmaza/dml Vim w.v. imm@ Patented Dec. 2l, 1948 "455,844 massoni: SWITCH Norman J. Smith', Medileld, Mass., assigner to Smith Control and AInstrument Corporation, Needham, Mass.; a corporation of Massachusetts Application April 12, 1946, Serial N0. 661,500

(Cl. 20o-83) 14 claims. l

This invention relates to improvements in a pressure switch and more particularly to a pressure switch for opening or closing electrical circuits generally associated with the control and protection of pressure equipment.

In my prior Patent 2,441,725, dated May 18, 1.948, for improvements in thermostatic switch, I have shown a switch responsive to temperature. The present application incorporates certain features of my prior disclosure to a pressure switch.

A pressure switch of the type, to which this invention pertains, essentially comprises a casing or housing generally tubular at one end of the casing and a head at the other end containing a means for biasing the cooperable contacts carried within the Acasing to opened or closed position as desired. The pressure sensitive diaphragm is so connected to the cooperable contacts that a small movement -of the diaphragm will produce a relative multiplied movement between the contacts in a direction transverse to the axis of the casing.

A general object of the invention is to provide a compact pressure switch having a greatly multiplied lateral movement of the electrical contacts for a small longitudinal movement of the pressure sensitive diaphragm.

Another object of the invention is to provide a universal pressure switch capable of being adjusted over wide ranges of both pressure and vacuum.

Still `another object provides for biasing the electrical contacts in either a normally closed or normally opened position.

A further object allows a normal amount of unrestrained movement of the diaphragm without further movement of the electrical contacts after separation or closure has been effected.

Still further, the invention incorporates a protective feature limiting the travel of the diaphragm to prevent distortion of the internal members when the switch is accidentally subjected to pressures in excess of those specified.

Additional objects and advantages of other improvements will be more readily apparent from the following description of the two preferred embodiments of my invention as disclosed in the attached drawings, in which:

Fig. 1 is a longitudinal sectional view of a pressure switch which may be adjusted to close an electrical circuit on a decrease in pressure applied to the diaphragm or may be adjusted to open an electrical circuit on an increase in pressure applied to the diaphragm;

Fig. 2 is an end view of the switch shown in Fig. 1;

Fig. 3 is a fragmentary longitudinal sectional view of a switch similar to that disclosed in Fig. 1 but showing a modied arrangement of the struts; and

Fig. 4 is a fragmentary longitudinal sectional view showing a further modification of the switch which may be adjusted to close an electrical circuit on an increase in pressure applied to the diaphragm or to open an electrical circuit on a decrease in pressure applied to the dia-- phragm.

Referring to Fig. l, there is shown a casing or housing III having a pressure sensitive diaphragm I2 retained in operable alignment with the bore I4 of housing I 0 by a flanged coupling I6 and screws I8. The vdiaphragm I2 constitutes a corrugated thin metallic plate 20 retained by a stud or rivet 22 between the beveled washers 24 and 26, seatable against the shoulders 28 and 30 when excess pressure or vacuum is applied to the da# phragm I2. On the inner side of the diaphragm I2 is mounted a strut 32 having an extension 34 on which a clip 36 carrying contact 36 is fastened. The contact 38 is spaced from electrical contact with the clip 36 by insulation 40. The strut 32 extends from the diaphragm I2 toward the opposite end of the casing Ill and is reversely bent near said upper end to form a U-shaped member comprising an arc or bow 42 intermediate substantially parallel legs 44 and 46. The U-shaped member 42-44-46 need not be so shaped since it may be formed as shown at |02 in Fig. 3 as I later describe on some other page may be employed, it being understood that this member constitutes a substantially rigid compression or tension member to produce the desired leverage.

Threaded into the head 48, which is ailixed to the casing I0 by screws 50, is an adjusting bolt or screw 52 having a relatively coarsely threaded external section 54 and an internal socket receiving a finelythreaded section 56 of stud 58, the stud 58 being rigidly secured to the resilient dog 60 which is an integral part of the head 48.

Turning adjusting bolt 54 in a clockwise direction will cause the bolt 52 to thread into the headV 48 and the stud 58 to thread into the bolt 52 at a slower rate which will cause the stud 58 to move towardgthe diaphragm I2 to deflect the is fastened and is separated from the leaf spring l2 by insulation 08. To contacts 38 and 60 are attached flexible cables 10 and 12 which emerge from the casing I0 through the grommet 14. The leaf spring 02 has a pair of slots 'I6 and 'IB receiving pins 00 and 82 which slidably retain the leg 46 of strut 32 against the leaf spring 62. The pin 80 also provides a rigid reinforcement for the arc 42 by retaining tubular spacer 84 in a fixed position intermediate the legs 44 and 46.

A clockwise turning of the adjusting bolt 52 will cause the stud 50 to move towards the diaphragm I2 and deflect the dog 00 inwardly of the casing and move the leaf spring 82 until the lost motion of slots 18 and 'I8 is taken up and the thrust will deflect the leaf spring 62 in a direc tion to effect a separation of the contact 66 from the contact 38. An outward movement of the diaphragm I2, as will result from a decrease in pressure, will cause tension in the leg 44 of strut 32 and a movement of the tubular spacer 84 which acts as a short lever arm to allow the leaf spring 82 which acts as a long lever arm to spring the electrical contact 66 into engagement with the contact 38. After the contacts 38 and 6E have been closed, a further outward movement of the diaphragm I2 will merely allow the pins 80 and l2 to freely slide in the slots 1E and 18, the engagement of the contacts 38 and 6E being main tained by the spring action imposed on the leaf spring 62 by the action of the tubular spacer or short lever arm I4. An excessive outward move ment of the diaphragm will result in the beveled washer 24 abutting against the shoulder 28 before the pins 80 and l2 travel the entire length of their respective slots I6 and 18.

To bias the electrical contacts 38 and 6B in a closed position so that they will open on an increase in pressure, the adjusting bolt 54 must be turned in a counter clockwise direction until the inner ends of the slots 16 and 'I8 have engaged the pins 00 and 02. An increase in pressure against the diaphragm will then result in a compression of the leg 44 which will cause the tubular spacer or short lever arm 84 to pivot and cause the leaf spring or long lever arm 62 to deflect, so that the contact 6B will tend to separate from the contact 38. Here again, after separation of the contacts further movement of the diaphragm will merely cause the pins 80l and 82 to freely slide in the slots 16 and I8 until the beveled washer 26 abuts against the shoulder 30 and stops further movement, as would be the case when an excessive pressure is applied against the diaphragm I2.

Referring to Fig. 3, there is shown another embodiment of the invention in which the same reference numerals are used in so far as possible, since the construction is quite similar to that in Fig. 2. In this arrangement the U-shaped strut l2 is replaced by the strut |00 having angularly disposed section |02 terminating against strip |04 which is held against the leaf spring 62 by the pins 80 and 02 slidably received in the slots IB and 10. The upper end of the leaf spring 62 is non-rotatably held to the clevis |06 by pin |08 having one end slidably received by a longitudinal slot I I0 in stud l I2 which is fastened to the head 4l by a rivet I I4. The threaded section IIB of the clevis |00 is received by the adjusting bolt 52 which is in turn threaded into the head I8 as in Fig. 1. Longitudinal movement of the leaf spring B2 is permitted by the pinl08 sliding in the slot IIO without rotation of the clevis |06 when the adjusting bolt 52 is turned.

The switch as so far described is capable of adjustment to operate on an increase in pressure or a decrease in pressure it being understood that it could also operate under vacuum by an increase or decrease in the vacuum. In one adjustment, the contacts are initially biased to closed position and upon an increase in the pressure on the diaphragm, the contacts will be opened thereby opening the electrical circuit. The switch may also be adjusted to bias the contacts to opened position whereby a decrease in pressure applied to the diaphragm will close the contacts and complete the electrical contact. It may be desired to obtain just the reverse operation; that is, a switch which will close the electrical circuit on an increase in pressure or will open the electrical circuit on a decrease in pressure. To carry out this function, the switch may be designed as shown in Fig. 4 in which the U-shaped member comprising the legs 44 and 4E is the same as in Fig. 1 but a contact I20 is fastened to the ieg 44 by the clip I22 and separated therefrom by insulation |24. 'I'he member 44 is connected to the diaphragm by the rivet 22. The leg 46 of' the U-shaped member is attached to the leaf spring B2 as in Fig. l and carries a contact I20 fastened by clip |28 and insulated from the part B2 by insulation |30. It will be evident that in this arrangement the adjusting screw 54 must be turned in to bias the contacts to closed position while moving the screw outward will bias the.

contacts to opened position. After contacts are initially biased to closed position, then a decrease in pressure will open the contacts; Whereas if the contacts are initially biased to opened position an increase in pressure will close the contacts.

The switch as shown in Fig. l may be adjusted by the screw 54 to bias the leaf spring of st'rut B2 and initially close the contacts. .'Ihat is, the leaf spring 62 will be sprung adjacent its mounting on the linger 60 so that the contacts are held closed and the strut structure from the daphragm will be placed under tension whereby an increase in. pressure on the diaphragm is required to relieve the tension and permit the contacts to open. If, on the other hand, the adjusting screw 54 is initially turned to bias the leaf spring or strut 62 in a direction to open the contacts. the strut structure from the diaphragm will be placed under compression and decrease in pressure on the diaphragm will be required to relieve the compression and permit the contacts to close. The modified construction of the switch as in Fig. 4 will similarly be adjusted to tension or compression but the action will be just the reverse.

While I have shown and described preferred embodiments of my invention, I do not wish to be limited thereto as the invention is capable of modification within the scope of the appended claims.

I claim:

l. In a pressure switch, a housing, a pressure sensitive diaphragm, a resilient leaf spring mounted in said housing, a contact carried by the free end of said leaf spring, a Contact adapted to be engaged by said first mentioned contact, a member having one end mounted on said diaphragm and means engaging the other end of said member with said leaf spring for causing a relative movement between said contacts by a variation in the pressure upon the diaphragm.

2. In a pressure switch, a housing, a pressure sensitive diaphragm, a relatively short strut 5 mounted on said diaphragm, a contact carried by said strut, a relatively long strut forming a U-shaped member having one leg mounted on said diaphragm and a reversely bent second leg resiliently attached to said housing, a contact carried by the long strut cooperable with the flrst by said strut, a`relatively long strut forming a' U-shaped member having one leg mounted on said diaphragm and -a second leg resiliently at` tached to said housing, a contact carried by the long strut cooperable with the iirst mentioned contact, whereby the abutments of said diaphragm will seat against the shoulders of said housing to prevent damage from excessive pressure or vacuum.

4. In a pressure switch, a casing having a head at one end, a pressure sensitive diaphragm mounted at the other end, a relatively short-strut mounted on said diaphragm and extending toward the head of said casing, a contact carried by said strut, a relatively long strut forming a resilient U-shaped member composed of one leg mounted on said diaphragm which extends towards said head and areversely bent second leg which projects back towards said diaphragm, a contact carried by the long strut cooperable with the first mentioned contact, a resilient strip having one end adjustably mounted on the head of said casing and the other end engageable near said head with the reversely bent leg of said long strut, said long strut being initially biased toward separation of said contacts by engagement of said resilient strip with said reversely bent leg and means for longitudinally adjusting the mounting of said resilient strip with respect to said head to cause said contacts to close, whereby said contacts will open at a predetermined increased pressure on the diaphragm.

5. In a pressure switch, a casing having a head at one end, a pressure sensitive diaphragm mounted at the other end, a relatively short strut mounted on said diaphragm and extending to-v ward the head of said casing, a contact carried by said strut, a relatively long strut forming a resilient U-shaped member composed of one leg mounted on said diaphragm which extends towards said head and a reversely bent second leg which projects back towards said diaphragm, a contact carried by the longer strut cooperable with the first mentioned contact, a resilient strip having one end adjustably mounted on the head of said casing and the other end engageable near said head with the reversely bent leg of said longer strut, said longer strut being initially biased toward closure of said contacts by engagement of said resilient strip with said reversely bent leg, means for longitudinally adjusting the mounting of said resilient strip with respect to said head to cause said contacts to open, whereby said contacts will close at a predetermined reduced pressure on the diaphragm.

6. A pressure switch for an electrical circuit comprising a casing having a head at one end, a pressure sensitive diaphragm mounted at the other end, a relatively short strut and a relatively long U-shaped strut mounted on said diaphragm, a pair of cooperable contacts carried by said struts near said diaphragm, a resilient strip having a slot in one end and having the other end mounted on the head of said casing, means re. ceived by said slot for slidably retaining said resilient strip to said U-shaped strut near said head, whereby a longitudinal movement of said diaphragm will produce a multiplied vlateral movement between said contacts up to a predetermined point after which further lateral movement ceases as said means'is then free to move with respect to said slot. y

7. In a pressure switch, a housing, a pressure sensitive diaphragm, a substantially rigid L- shaped member having relatively long and short lever arms, means resiliently mounting said member within said housing, a contact carried by the long lever arm of said member, a contact adapted to be engaged by said rst mentioned contact and means connecting said diaphragm to the short lever arm of said member for causing relative movement between said contacts at a predetermined pressure. i

8. In a pressure switch, a casing having a head, a resilient dog integral with said head, a pressure sensitive diaphragm, a pair of contact carrying struts movable by said diaphragm to cause a relative movement of said contacts, means connecting one of said struts to said dog, an adjusting screw threaded into said head, a second screw rigidly mounted on said dog and threaded into said adjusting screw, said adjusting screw having relatively coarse external threads and fine internal threads to engage the second screw whereby an inward turning of said adjusting screw will result in a slower inward movement of said second screw to cause a precise deiiection of said dog and a resulting biased 'position of said contacts.

9. In a pressure switch, a casing having a head, a pressure sensitive diaphragm, a pair of contact carrying struts movable by said diaphragm to cause relative movement between said contacts, an adjusting screw threaded into said head, a second screw threaded into said adjusting screw, means connecting one of said struts to said second screw and means mounted on said head for holding said second screw against rota tion when biasing said contacts.

10. In a pressure switch, a pressure sensitive diaphragm, a first strut movable by said diaphragm, a second strut resiliently mounted at one end and forming a long lever arm, means connecting the first strut to said second strut near the resiliently mounted end therof whereby the force transmitted through said first strut by movement of the diaphragm is applied at an angle to said second strut to form in effect a short lever arm, a first electrical contact carried by said second strut at its end opposite to the resiliently mounted end and a second electrical contact cooperable with said flrst contact.

11. In a pressure switch, a pressure sensitive diaphragm, a first strut movable by said diaphragm, a second strut resiliently mounted at one end and forming a longlever arm, means connecting the rst strut to said second strut near the resiliently mounted end thereof whereby the force transmitted through said ilrst strut by movement of the diaphragm is applied at an angle to said second strut to form in effect a short lever arm, a iirst electrical contact carried by said second strut at its end` opposite to the resiliently mounted end and a. second 'electrical contact cooperable with said .first contact, and

means for biasing the second strut to initially close the contacts whereby the contacts will open at a desired degree ot the pressure.

12. In a pressure switch, a pressure sensitive diaphragm. a ilrst strut movable by said diaphragm, a second strut resiliently mounted at on end and forming a long lever arm, means connecting the i'irst strut to said second strut near the resiliently mounted end thereof whereby the force transmitted through said first strut by movement of the diaphragm is applied at an angle to said second strut to form in effect a short lever arm, a first electrical contact carried by said second strut at its end opposite to the resiliently mounted end and a second electrical contact cooperable with said tlrst contact, and means for biasing the second strut to openthe contacts whereby the contacts will close at a desired degree of pressure.

13. In a pressure switch, a pressure sensitive diaphragm. a Ilrst strut movable by said diaphragm, a second strut resiliently mounted at one end and forming a long lever arm, means connecting the rst strut tosaid second strut near the resiliently mounted end thereof whereby the force transmitted through said rst strut by movement of the diaphragm is applied at an angle to said second strut to form in effect a short lever arm, a ilrst electrical contact carried by said second strut at its end opposite to the resiliently mounted end and a second electrical contact cooperable with said first contact. and means for biasing the second strut to place the first strut under compression whereby decrease in pressure on the diaphragm will relieve the compression and cause relative movement between the contacts.

14. In a pressure switch, a pressure sensitive diaphragm, a first strut movable by said diaphragm. a second strut resiliently mounted at one end and forming a long lever arm, means connecting the first strut to said second strut near the resiliently mounted end thereof whereby the force transmitted through said first strut by movement of the diaphragm is applied at an angle to said second strut to form in eiIect a short lever arm, a ilrst electrical contact carried by said second strut at its end opposite to the resiliently mounted end and a second electrical contact cooperable with said first contact, means for biasing the second strut to place the iirst strut under tension whereby an increase in pressure upon the diaphragm will relieve the tension and cause relative movement between the contacts.

NORMAN J. Sm.

REFERENCES CITED The following references are of record in the ille `oi' this patent:

UNITED STATES PATENTS Number Name .Date

1,555,419 Kimmel et al M Sept. 29, 1925 2,257,990 Turenne Oct., 7, 1941 

